In the prior art, there are known devices for perforation of wells by piercing, disclosed in Russian Federation Patents RU 2129655 C1, IPC 6 E21B 43/112, 27 Apr. 1999; RU 2355877 C2, IPC E21B 43/112, 20 May 2009, including a casing, tool pistons with piercing elements—punchers with a mechanism of their extension, which is based on the principle of fluid expansion during heating and making of its high-pressure supplied to the tool pistons, as a result a radial moving of the tool pistons and an extension of the punchers happen. Significant disadvantages of these devices are low productivity, insecurity and design complexity, including energy drive with a heat source. Moreover, such perforator designs exclude a jetting process possibility of a critical area of formation immediately after an opening up of the column, which reduces the efficiency of the opening up.
In the prior art a large number of piercing perforating devices are known, their method of operation is based on the extension of pushers by hydraulic mechanisms disclosed in Russian Federation Patents: RU 2373382 C1, IPC E21B 43/112, 20 Nov. 2009; RU 2172394 C1, IPC 7 E21B 43/112, 20 Aug. 2001; RU 2069741 C1, IPC 6 E21B 43/112, 27 Nov. 1996; RU 2069740 C1, IPC 6 E21 B 43/112, 27 Nov. 1996, RU 2043486 C1, IPC 6 E21B 43/114, 10 Sep. 1995. The devices include a casing, comprising a system of chambers, pistons and rods, leading the working fluid coming to the perforator through the column of tubings to the punch piston. Such hydraulic mechanisms often have a low penetration. In order to increase the penetration they can include pressure boosters, which complicate the devices' design and increase manufacturing costs, the productivity and efficiency of the devices are not high enough at the same time. Moreover, when using such perforators with boost pressures the tightness problems of all design units and accelerated wear of seal elements of the pistons are arisen.
In the prior art, there is known a device for creating perforating channels in a casing string according to Russian Federation Patent RU 2395671 C1, IPC E21B 43/112, 27 Jul. 2010. The device comprises a tube and support housings, a cylinder connected to the support housing and comprising an actuating piston with a return spring and a slip pusher, equipped with working cutters longitudinally moveable in relation to the slip pusher when actuated by the support housing, a valve gear with its casing, mounted above the cylinder, and a secondary return spring, and the tube housing is connected to the piston to perform a constrained longitudinally movement. The cylinder above the support housing is provided with a ring seat, the piston has a collar, and the return spring is mounted between the external collar of the piston and the ring seat of the cylinder. The tube housing has a seat above the ring collar of the piston, while the secondary return spring is mounted between the seat and the piston in the cylinder. The casing of the valve gear is fixedly connected with tube housing and it has a valve seat at the top and an unsealed internal seat at the bottom. The spring is applied to press the valve to the seat of the valve gear casing from the internal seat, so that to hold a liquid column forcing the valve in the perforation interval.
The connection of the valve gear and tube housing can be made built-up (for example, a thread) for convenience of assembling and disassembling. The number of cylinders and their respective actuating pistons is selected based on forces necessary for the opening up of the casing string of the well: the thicker wall of the casing string, the greater a number of cylinders with the actuating pistons need to be used. Unauthorized overflows of liquid in the device are excluded by seals.
This device has no disadvantages of hydraulic piercing-type perforators, it has a high punch capability, sufficient power and it opens up the column effectively, but its design excludes the jetting process possibility of a critical area of formation immediately after the opening up of the column, which reduces the efficiency of the opening up.
To offer a more powerful device for drilling-in the effort is made in the useful model according to Russian Federation Patent RU 115407 U1, IPC E21B 43/114, 27 Apr. 2012. This device is the closest analog of the proposed invention and it is herein further referred to as a ‘prototype’.
The prototype device for creating of perforating channels in the well comprises a casing, a wedge with grooves, at least two hydraulic cylinders placed one behind the other with connected piston rods, one of which is spring-loaded, and at least two cutters with jets and cutters' holders, placed in grooves of a support and a wedge with an ability of radial reciprocating moving, the casing is made by the wedge and walls of the hydraulic cylinders, in which the piston rods are made with an axial channel connected downpipe with their piston cavities and with tubes of cutters' jets through channels in the cutters' holders, the support of which is connected to the piston rod, which is spring-loaded downward relative to the hydraulic cylinder.
The disadvantage of the device according to the prototype is unreliability of the design of the working fluid supply in the jet nozzle. There is a high probability of a pipe break or seal failure of the pipes in operating conditions; therefore not only caverns washout would be impossible to execute, but also the column opening, because the working fluid from the hydraulic cylinders would flow through the tube during creating an operating pressure. This can lead to an emergency in the well.